Device and method of reducing ESD damage in thin film read heads which enables measurement of gap resistances and method of making

ABSTRACT

A first read gap layer has a resistance R G1  between a first shield layer and one of the first and second lead layers of a read head and the second read gap layer has a resistance R G2  between a second shield layer and said one of the first and second lead layers of the read head. A connection is provided via a plurality of resistors between a first node and each of the first and second shield layers wherein the plurality of resistors includes at least first and second resistors R S1  and R S2  and the first node is connected to said one of the first and second lead layers. A second node is located between the first and second resistors R S1  and R S2 . An operational amplifier has first and second inputs connected to the first and second nodes respectively so as to be across the first resistor R S1  and has an output connected to the first node for maintaining the first and second nodes at a common voltage potential. In a first embodiment the first and second shield layers are shorted together. A test instrument is then employed for determining the combined parallel resistance of the resistors R S1  and R S2  by having a first side of the test instrument connected to the first node and the second side connected to each of the first and second shield layers. In the second embodiment a third resistor R S3  is connected between the second node and one of the shield layers, such as the second shield layer. The test instrument can determine the resistances of the first and second gap layers separately by being connected between the first node and the first shield layer for the resistance of the first gap layer or between the first node and the second shield layer for the resistance of the second gap layer.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a device for reducingelectrostatic discharge (ESD) damage in thin film read heads whichenables measurement of gap resistances and, more particularly, to such adevice and method wherein the resistance of first and second gap layerscan be measured in parallel or the resistance of each of the first andsecond gap layers can be measured separately.

[0003] 2. Description of the Related Art

[0004] The heart of a computer is a magnetic disk drive which includes arotating magnetic disk, a slider that has read and write heads, asuspension arm above the rotating disk and and actuator arm that swingsthe suspension arm to place the read and write heads over selectedcircular tracks on the rotating disk. The suspension arm biases theslider into contact with the surface of the disk when the disk is notrotating but, when the disk rotates, air is swirled by the rotating diskadjacent an air bearing surface (ABS) of the slider causing the sliderto ride on an air bearing a slight distance from the surface of therotating disk. When the slider rides on the air bearing the write andread heads are employed for writing magnetic impressions to and readingmagnetic signal fields from the rotating disk. The read and write headsare connected to processing circuitry that operates according to acomputer program to implement the writing and reading functions.

[0005] An exemplary high performance GMR read head employs a spin valvesensor for sensing the magnetic field signals from the rotating magneticdisk. First and second leads are connected to the spin valve sensor forconducting a sense current therethrough. The sensor and the first andsecond leads are located between first and second dielectric read gaplayers which are, in turn, located between ferromagnetic first andsecond shield layers. Accordingly, the GMR head is electrically isolatedfrom the two shields by the first and second gap layers which aretypically aluminum oxide (Al₂O₃). The gap length, which is the distancebetween the shield layers, is continually being shortened in order toachieve higher areal density. For a given sensor thickness, therefore,the gap layers have to become thinner. In head designs, the shields aretypically not electrically connected to any other conductors on theslider, and are electrically isolated from each other. As a result, acharge may accumulate on the shields during processing. The presence ofthis charge causes a potential difference across the gap layers. Whenthis voltage reaches a sufficiently high value, the dielectric breaksdown, and electrical shorts can occur at the location of the breakdown.This is a type of electrostatic discharge (ESD) damage. Shorts betweenthe sensor and the shields are detrimental to the operation of the head.A typical specification on the resistance between the shields and thesensor is 100 kOhms. Accordingly, any head with a resistance less than100 kOhms between the read sensor and either shield fails such a test.Losses at wafer final test due to shield shorts can be as high as 30%.One way to prevent the charging of the shields is to electrically shortboth shields to one side of the sensor via a lead and then remove theshort during slider fabrication. While this will provide protectionagainst process-induced charging, it does not allow the ability to testfor shield shorts due to other phenomena, such as pinholes in the gapdielectric.

SUMMARY OF THE INVENTION

[0006] The present invention provides a device and method of reducingESD damage to the sensor of the read head while enabling measurement ofthe first and second gap resistances. The first read gap layer can beconsidered to have a resistance R_(G1) between the first shield layerand one of the first and second lead layers and the second read gaplayer can be considered to have a resistance R_(G2) between the secondshield layer and one of the first and second lead layers. A short isprovided via a plurality of resistors between a first node and each ofthe first and second shield layers wherein the plurality of resistorsincludes at least first and second resistors R_(S1) and R_(S2) and thefirst node is connected to either one of the first and second leads. Asecond node is located between the first and second resistors R_(S1) andR_(S2). An operational amplifier has first and second inputs connectedto the first and second nodes respectively so as to be across the firstresistor R_(S1) and has an output connected to the first node formaintaining the first and second nodes at a common voltage potential.

[0007] In one embodiment of the invention the first and second shieldlayers are shorted together. In this embodiment a test instrument can beemployed for determining the combined parallel resistance of the firstand second gap layers by having a first side of the test instrumentconnected to the first node and a second side connected to each of thefirst and second shield layers. In another embodiment of the inventionthe second resistor R_(S2) is connected between the second node and theshield layer and a third resistor R_(S3) is connected between the secondnode and the first shield layer. In this embodiment the test instrumenthas a first side connected to the first node and a second side connectedto the first shield layer for determining the resistance of the firstgap layer separately. Alternatively, the test instrument can be employedwith its first side connected to the first node and its second sideconnected to the second shield layer so that the resistance of thesecond gap layer can be determined separately. In another aspect of theinvention the sensor and the resistors R_(S1) and R_(S2) or R_(S1),R_(S2) and R_(S3) are coplanar. This is accomplished by forming a layerof sensor material on a wafer and then patterning the layer of materialto individually form the sensor and each of the resistors. The formationof the sensor material layer can be by sputter deposition and thepatterning may be accomplished by photolithography.

[0008] An object of the present invention is to reduce ESD damage to thesensor of a read head while enabling measurement of gap resistances inparallel or separately.

[0009] Another object is to accomplish the foregoing object with thesensor and a plurality of resistors patterned from a common materiallayer wherein the plurality of resistors are in parallel with theresistances of the first and second gap layers.

[0010] Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a plan view of an exemplary magnetic disk drive;

[0012]FIG. 2 is an end view of a slider with a magnetic head of the diskdrive as seen in plane 2-2 of FIG. 1;

[0013]FIG. 3 is an elevation view of the magnetic disk drive whereinmultiple disks and magnetic heads are employed;

[0014]FIG. 4 is an isometric illustration of an exemplary suspensionsystem for supporting the slider and magnetic head;

[0015]FIG. 5 is an ABS view of the magnetic head taken along plane 5-5of FIG. 2;

[0016]FIG. 6 is a partial view of the slider and a piggyback magnetichead as seen in plane 6-6 of FIG. 2;

[0017]FIG. 7 is a partial view of the slider and a merged magnetic headas seen in plane 7-7 of FIG. 2;

[0018]FIG. 8 is a partial ABS view of the slider taken along plane 8-8of FIG. 6 to show the read and write elements of the piggyback magnetichead;

[0019]FIG. 9 is a partial ABS view of the slider taken along plane 9-9of FIG. 7 to show the read and write elements of the merged magnetichead;

[0020]FIG. 10 is a view taken along plane 10-10 of FIGS. 6 or 7 with allmaterial above the coil layer and leads removed;

[0021]FIG. 11 is an enlarged isometric illustration of a read head whichhas a spin valve sensor;

[0022]FIG. 12 is a circuit diagram of one embodiment of the presentinvention;

[0023]FIG. 13 is the same as FIG. 12 except a test instrument isemployed to measure the combined parallel resistance of the first andsecond gap layers;

[0024]FIG. 14 is a circuit diagram of a second embodiment of the presentinvention with the test instrument measuring the combined parallelresistance of the first and second gap layers;

[0025]FIG. 15 is a circuit diagram of a third embodiment of the presentinvention with the test instrument measuring the resistance of only thefirst gap layer;

[0026]FIG. 16 is the same as FIG. 15 except that the test instrument ismeasuring the resistance of only the second gap layer;

[0027]FIG. 17 is an isometric illustration of rows and columns ofmagnetic heads on a wafer substrate; and

[0028]FIG. 18 is an exemplary plan layout of the embodiments shown inFIGS. 12, 13 and 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

[0029] Referring now to the drawings wherein like reference numeralsdesignate like or similar parts throughout the several views, FIGS. 1-3illustrate a magnetic disk drive 30. The drive 30 includes a spindle 32that supports and rotates a magnetic disk 34. The spindle 32 is rotatedby a spindle motor 36 that is controlled by a motor controller 38. Aslider 42 has a combined read and write magnetic head 40 and issupported by a suspension 44 and actuator arm 46 that is rotatablypositioned by an actuator 47. A plurality of disks, sliders andsuspensions may be employed in a large capacity direct access storagedevice (DASD) as shown in FIG. 3. The suspension 44 and actuator arm 46are moved by the actuator 47 to position the slider 42 so that themagnetic head 40 is in a transducing relationship with a surface of themagnetic disk 34. When the disk 34 is rotated by the spindle motor 36the slider is supported on a thin (typically, 0.05 μm) cushion of air(air bearing) between the surface of the disk 34 and the air bearingsurface (ABS) 48. The magnetic head 40 may then be employed for writinginformation to multiple circular tracks on the surface of the disk 34,as well as for reading information therefrom. Processing circuitry 50exchanges signals, representing such information, with the head 40,provides spindle motor drive signals for rotating the magnetic disk 34,and provides control signals to the actuator for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a suspension44. The components described hereinabove may be mounted on a frame 54 ofa housing 55, as shown in FIG. 3.

[0030]FIG. 5 is an ABS view of the slider 42 and the magnetic head 40.The slider has a center rail 56 that supports the magnetic head 40, andside rails 58 and 60. The rails 56, 58 and 60 extend from a cross rail62. With respect to rotation of the magnetic disk 34, the cross rail 62is at a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

[0031]FIG. 6 is a side cross-sectional elevation view of a piggybackmagnetic head 40, which includes a write head portion 70 and a read headportion 72, the read head portion employing a sensor 74. FIG. 8 is anABS view of FIG. 6. The sensor 74 is sandwiched between nonmagneticelectrically insulative first and second read gap layers 76 and 78, andthe read gap layers are sandwiched between ferromagnetic first andsecond shield layers 80 and 82. In response to external magnetic fields,the resistance of the sensor 74 changes. A sense current I_(S) conductedthrough the sensor causes these resistance changes to be manifested aspotential changes. These potential changes are then processed asreadback signals by the processing circuitry 50 shown in FIG. 3.

[0032] The write head portion 70 of the magnetic head 40 includes a coillayer 84 sandwiched between first and second insulation layers 86 and88. A third insulation layer 90 may be employed for planarizing the headto eliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. An insulation layer 103 is locatedbetween the second shield layer 82 and the first pole piece layer 92.Since the second shield layer 82 and the first pole piece layer 92 areseparate layers this head is known as a piggyback head. As shown inFIGS. 2 and 4, first and second solder connections 104 and 106 connectleads from the sensor 74 to leads 112 and 114 on the suspension 44, andthird and fourth solder connections 116 and 118 connect leads 120 and122 from the coil 84 (see FIG. 10) to leads 124 and 126 on thesuspension.

[0033]FIGS. 7 and 9 are the same as FIGS. 6 and 8 except the secondshield layer 82 and the first pole piece layer 92 are a common layer.This type of head is known as a merged magnetic head. The insulationlayer 103 of the piggyback head in FIGS. 6 and 8 is omitted.

[0034]FIG. 11 is an isometric ABS illustration of the read head 72 shownin FIGS. 6 or 8. The read head 72 includes the spin valve sensor 74.First and second hard bias and lead layers 134 and 136 are connected tofirst and second side edges 138 and 140 of the sensor. This connectionis known in the art as a contiguous junction and is fully described incommonly assigned U.S. Pat. No. 5,018,037 which is incorporated byreference herein. The first hard bias and lead layers 134 include afirst hard bias layer 140 and a first lead layer 142 and the second hardbias and lead layers 136 include a second hard bias layer 144 and asecond lead layer 146. The hard bias layers 140 and 144 cause magneticfields to extend longitudinally through the sensor 74 for stabilizingthe magnetic domains therein. The sensor 74 and the first and secondhard bias and lead layers 134 and 136 are located between nonmagneticelectrically insulative first and second read gap layers 148 and 150.The first and second read gap layers 148 and 150 are, in turn, locatedbetween ferromagnetic first and second shield layers 152 and 154.

[0035] The gap length, which is the distance between the first andsecond shield layers 152 and 154 in FIG. 11, determines the linear bitread density of the read head. The linear bit density is quantified asbits per inch (BPI) which is the number of bits that can be read by theread head along an inch of a track on a rotating magnetic disk. Thewidth of a free layer (not shown) in the sensor 74 defines the trackwidth of the read head. The track width density is quantified as thenumber of tracks per inch (TPI) along a radius of the rotating magneticdisk. The product of the linear bit density and the track width densityis the areal density of the read head. The higher the areal density, thehigher the storage capacity of the magnetic disk drive.

[0036] In order to increase the linear bit density it is necessary todecrease the thicknesses of the first and second gap layers 148 and 150.When these gap layers are made thinner there is a risk of a pinhole in agap layer which permits an electrostatic discharge (ESD) to occurbetween either of the first and second shield layers and the sensor 74or either of the first and second lead layers 134 and 136. An ESD candestroy the spin valve sensor 74 rendering the read head inoperable. Acharge can build up on either of the first and second shield layers 152or 154 by human handling or contacting a charged object which istypically made of plastic. The risk of an ESD is primarily duringfabrication of the magnetic head and mounting it on a magnetic diskdrive. After mounted on a magnetic disk drive the risk of an ESD isminimal. In order to minimize ESD damage to the read sensor 74 the firstand second shield layers 150 and 154 may be shorted to either of thelead layers 134 and 136. After assembly of the magnetic head on amagnetic disk drive the short may be deleted by severing a delete pad onthe surface of the slider with a laser beam. Alternatively, thecircuitry for the short may be lapped away at a row level of magneticheads before dicing the row into individual heads and assembly on themagnetic disk drive. While a short between the first and second shieldlayers and either one of the first and second lead layers 134 and 136minimizes ESD damage to the sensor 130, there has been no provision fordetermining the resistances of the first and second gap layers 148 and150 and rejecting heads which have low resistances due to pinholes ineither of the gap layers.

First Embodiment of the Invention

[0037] A first embodiment 200 of the present invention is shown in FIG.12 which shows the first and second lead layers 134 and 136 (L1 and L2)connected to the read sensor 74. The sensor 74 is shown as having aresistance R_(MR). FIG. 12 also shows the first and second shield layersS1 and S2 80 and 82 are shorted by a lead 202. First and secondresistors 204 and 206 are connected across the second lead L2 and thefirst and second shield layers S1 and S2. With this arrangement thefirst read gap layer 76 has a resistance R_(G1), between the shieldlayers S1 and S2 and the second lead L2 and the second read gap layer 78has a resistance R_(G2) between the shield layers S1 and S2 and thesecond lead L2. Alternatively, the first and second resistors 204 and206 may be connected between the first and second shield layers S1 andS2 and the first lead layer L1. In this instance, the resistance R_(G1)would be the resistance between the shield layers S1 and S2 and thefirst lead layer L1 and the resistance R_(G2) would be the resistancebetween the shield layers S1 and S2 and the first lead layer L1. Acenter point (CP) is located between the first and second resistors 204and 206 which will be discussed in more detail hereinafter.

[0038]FIG. 13 is the same as FIG. 12 except a circuit tester 208 isconnected across the first and second shield layers S1 and S2 and thesecond lead layer L2. The circuit tester 208 applies a predeterminedvoltage or a predetermined current and then reads the current or thevoltage respectively. Assuming the circuit tester 208 applies apredetermined voltage and reads the current, then the resistance of thecircuit, which is the parallel combination of R_(S1) plus R_(S2), R_(G1)and R_(G2), is the predetermined voltage divided by the current. Itshould be noted that no current flows through the sensor 74 since thefirst lead L1 is floating. The resistance value of the seriescombination R_(S1), plus R_(S2) can be made high enough so that it isroughly equal to or larger than any shield short of interest. Assuming,however, that the specification on shield shorts is 100 kOhm, aresistance that high may not offer sufficient protection from shieldcharging effects and would require a very long resistor. This problem isovercome in the second embodiment.

Second Embodiment of the Invention

[0039]FIG. 14 illustrates a second embodiment 300 of the presentinvention which is an improvement over the first embodiment 200 in FIG.13. The embodiment 300 is the same as the embodiment 200 except for thefollowing. The center point (CP) has two separate connections 302 and304. The second lead L2 can be considered as a first node in the circuitand the connection 302 can be considered as a second node. Anoperational amplifier 306 has a first input 308 connected to the secondlead L2 (first node) and a second input 310 connected to the firstcontact 302 (second node). The output 312 of the operational amplifieris connected to the second contact 304 which is located between thefirst contact 302 and the second resistor 206. The operational amplifier306, which is configured as a unity gain buffer, is adjusted so that itdrives the center point (CP) between the resistors 204 and 206 to thesame potential as the second lead L2 (first node). As a result, there iszero voltage drop across the first resistor 204, which means that nocurrent will flow through the first resistor 204 nor through the secondresistor 206. This means that all of the current from the circuit tester208 will attempt to flow through the first and second gap layers 76 and78. With this arrangement the first and second resistors 204 and 206 donot need to be equal.

[0040] Assuming that the circuit tester 208 applies 2 volts between thesecond lead L2 and the shield layers S1 and S2, the potential of thenode at the center point (CP) will also rise to 2 volts. It is thereforehelpful to make the second resistor 206 large enough so that it does notdissipate an excessive amount of power which could cause the secondresistor 206 to melt. The value of the first resistor 204 is preferablysmaller than the resistance of the second resistor 206 so that theseries resistance R_(S1) plus R_(S2) is made as low as possible. Itshould be noted that the circuit tester 208 and the resistances 204 and206 can optionally be connected to the first lead L1 instead of thesecond lead L2 in which instance the resistances R_(G1), and R_(G2) willbe the resistances of the first and second gap layers 76 and 78 betweenthe first lead layer L1 and the first and second shield layers S1 andS2. It should further be noted that in either instance that theembodiment shown in FIG. 14 does not enable a determination of theresistances R_(G1) and R_(G2) of the first and second gap layers 76 and78 separately but, in contrast, measures these resistances in parallel,which parallel reading excludes the resistances R_(S1) and R_(S2) of theresistors 204 and 206 because of the operation of the operationalamplifier 306.

Third Embodiment of the Invention

[0041]FIG. 15 shows a third embodiment 400 of the present inventionwhich can measure the resistances R_(G1) and R_(G2) of the first andsecond gap layers 76 and 78 separately and is therefore an improvementover the embodiment 300 in FIG. 14. The embodiment 400 is the same asthe embodiment 300 in FIG. 14 except for the following. The first andsecond shield layers S1 and S2 are no longer shorted together and athird resistor 402 having a resistance R_(S3) is connected between thecenter point (second node) and the first shield layer S1. Theresistances R_(G1) and R_(G2) of the first and second gap layers 76 and78 can now be determined separately. The resistance R_(G2) of the secondgap layer 78 can be determined when the circuit tester 208 is connectedacross the second shield layer S2 and the second lead layer L2.Optionally, the resistance R_(G1) of the first read gap layer 76 can bedetermined by connecting the circuit tester 208 across the first shieldlayer S1 and the second lead layer L2, as shown in FIG. 16. Again, itshould be understood that since there is no current through the firstresistor 204 because of the operational amplifier 306 there is nocurrent through either of the resistors 206 and 402. Further, in eitherof the arrangements in FIGS. 15 and 16, the first lead L1 is floating.It should be further understood that all of the connections can be madebetween the first lead L1 instead of the second lead L2, as discussedhereinabove.

A Method of Making

[0042] Another aspect of the present invention includes a method ofmaking all of the aforementioned components. A still further aspect ofthe invention includes simultaneously patterning a sensor material layerfor forming the sensor 74 and the resistors 204 and 206 or the resistors204, 206 and 402. This may be accomplished by first depositing multiplefilms of the sensor 74 on a wafer, such as a wafer 500 in FIG. 17. Thesensor material layer may then be patterned by a positive photoresistwhich covers the MR sensor and the resistors which are to be retained.Ion milling then removes all of the sensor material layer except thatwhich is covered. The degree of covering the resistors determines theirresistances. This then enables the MR sensor and the resistors to besimultaneously formed, thereby saving fabrication steps. It should benoted that when this method is employed that the sensor 74 and theresistors 204 and 206 or the resistors 204, 206 and 402 will becoplanar. FIG. 17 shows rows and columns of magnetic heads 502 formedthereon. After completion of the magnetic heads 502 the wafer is dicedinto rows of magnetic heads and the rows are lapped to form the airbearing surface.

[0043]FIG. 18 shows an exemplary plan layout 700 of the embodimentsshown in FIGS. 12, 13 and 14. Lead layers 134 and 136 are shownconnected to the sensor 74 and first and second lead layer extensions150 and 152 interconnect the first and second lead layers 134 and 136 tothe pads 104 and 106, shown on the slider in FIG. 2, via first andsecond studs (not shown). The second lead layer 136 is connected to thefirst and second resistors 204 and 206 and the second resistor 206 isconnected to the first shield layer 80 (see FIG. 14) by a via 708. A pad710, which is shown in phantom, is located at the surface of the sliderand is interconnected to the center point (CP) between the resistors byone or more vias at 712. The first shield layer 80, shown in phantom, islocated below the sensor 74 and the first and second lead layers 134 and136 and is separated therefrom by the first read gap layer 76. After thesecond gap layer 78 is deposited a via 714 is formed down to the firstshield layer 80 so that when the second shield layer 82 is deposited ontop of the second read gap layer 78 the first and second shield layersare interconnected. During subsequent fabrication of the head a stud isprovided between the via 714 and a pad (not shown) at the surface of theslider. In practice the operational amplifier 306 is interconnected tothe pad 710 and the circuit tester 208 is interconnected between thesecond lead layer extension 152 and the pad to the via 714. As discussedhereinabove, the sensor 74 and the first and second resistors 204 and206 may be deposited simultaneously and patterned simultaneously.Alternatively, the sensor may be deposited and patterned separately andthe first and second resistors 204 and 206 may be depositedsimultaneously and patterned simultaneously. It should be understoodthat vias are simply holes in the structure that are filled with aconductive material such as copper. It should further be understood thatin the embodiment shown in FIG. 18 that after lapping a row of magneticheads all of the structure below an air bearing surface (ABS) of thesensor is removed. Alternatively, this structure may be on an oppositeside of the sensor in which case one or more delete pads at the surfaceof the slider may be severed by a laser beam to disconnect criticalportions of the test circuitry from the sensor.

[0044] Clearly, other embodiments and modifications of this inventionwill occur readily to those of ordinary skill in the art in view ofthese teachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A combination comprising: a read head including: a readsensor; first and second lead layers connected to the read sensor;nonmagnetic insulative first and second read gap layers with the readsensor and the first and second lead layers being located between thefirst and second read gap layers; ferromagnetic first and second shieldlayers with the first and second read gap layers being located betweenthe first and second shield layers; the first read gap layer having aresistance R_(G1) between the first shield layer and one of the firstand second lead layers and the second read gap having a resistanceR_(G2) between the second shield layer and said one of the first andsecond lead layers; a connection via a plurality of resistors between afirst node and each of the first and second shield layers wherein theplurality of resistors includes at least first and second resistorsR_(S1) and R_(S2) and the first node is connected to said one of thefirst and second lead layers; a second node located between the firstand second resistors R_(S1) and R_(S2); and an operational amplifierhaving first and second inputs connected to the first and second nodesrespectively so as to be across the first resistor R_(S1) and an outputconnected to the first node for maintaining the first and second nodesat a common voltage potential.
 2. A combination as claimed in claim 1wherein the sensor and the first and second resistances R_(S1) andR_(S2) are coplanar.
 3. A combination as claimed in claim 1 including: atest instrument for enabling a determination of resistance having afirst side connected to the first node and a second side connected to atleast one of the first and second shield layers.
 4. A combination asclaimed in claim 3 including: the first and second shield layers beingshorted together; and the second side of the test instrument beingconnected to each of the first and second shield layers.
 5. Acombination as claimed in claim 4 wherein the sensor and the first andsecond resistances R_(S1) and R_(S2) are coplanar.
 6. A combination asclaimed in claim 5 further comprising: a write head which includes: awrite head including: ferromagnetic first and second pole piece layersthat have a yoke portion located between a pole tip portion and a backgap portion; a nonmagnetic write gap layer located between the pole tipportions of the first and second pole piece layers; an insulation stackwith at least one coil layer embedded therein located between the yokeportions of the first and second pole piece layers; and the first andsecond pole piece layers being connected at their back gap portions. 7.A combination as claimed in claim 6 wherein the second shield layer andthe first pole piece layer are a common layer.
 8. A combination asclaimed in claim 6 wherein the second shield layer and the first polepiece layer are separate layers; and a nonmagnetic insulative isolationlayer located between the second shield layer and the first pole piecelayer.
 9. A combination as claimed in claim 1 including: the secondresistor R_(S2) being connected between the second node and the secondshield layer; and a third resistor R_(S3) being connected between thesecond node and the first shield layer.
 10. A combination as claimed inclaim 9 wherein the sensor and the first, second and third resistancesR_(S1), R_(S2) and R_(S3) are coplanar.
 11. A combination as claimed inclaim 9 including: a test instrument for enabling a determination ofresistance having a first side connected to the first node and a secondside connected to the first shield layer.
 12. A combination as claimedin claim 11 wherein the sensor and the first, second and thirdresistances R_(S1), R_(S2) and R_(S3) are coplanar.
 13. A combination asclaimed in claim 12 further comprising: a write head which includes: awrite head including: ferromagnetic first and second pole piece layersthat have a yoke portion located between a pole tip portion and a backgap portion; a nonmagnetic write gap layer located between the pole tipportions of the first and second pole piece layers; an insulation stackwith at least one coil layer embedded therein located between the yokeportions of the first and second pole piece layers; and the first andsecond pole piece layers being connected at their back gap portions. 14.A combination as claimed in claim 9 including: a test instrument forenabling a determination of resistance having a first side connected tothe first node and a second side connected to the second shield layer.15. A combination as claimed in claim 14 wherein the sensor and thefirst, second and third resistances R_(S1), R_(S2) and R_(S3) arecoplanar.
 16. A combination as claimed in claim 15 further comprising: awrite head which includes: a write head including: ferromagnetic firstand second pole piece layers that have a yoke portion located between apole tip portion and a back gap portion; a nonmagnetic write gap layerlocated between the pole tip portions of the first and second pole piecelayers; an insulation stack with at least one coil layer embeddedtherein located between the yoke portions of the first and second polepiece layers; and the first and second pole piece layers being connectedat their back gap portions.
 17. A method of making comprising the stepsof: making a read head including the steps of: forming a read sensor;forming first and second lead layers with the first and second leadlayers connected to the read sensor; forming nonmagnetic insulativefirst and second read gap layers with the read sensor and the first andsecond lead layers located between the first and second read gap layers;forming ferromagnetic first and second shield layers with the first andsecond read gap layers located between the first and second shieldlayers and the first read gap layer having a resistance R_(G1) betweenthe first shield layer and one of the first and second lead layers andthe second read gap having a resistance R_(G2) between the second shieldlayer and said one of the first and second lead layers; forming aconnection via a plurality of resistors between a first node and each ofthe first and second shield layers wherein the plurality of resistorsincludes at least first and second resistors R_(G1) and R_(G2), thefirst node is connected to said one of the first and second lead layersand a second node is located between the first and second resistorsR_(S1) and R_(S2); and connecting first and second inputs of anoperational amplifier to the first and second nodes respectively so asto be across the first resistor R_(S1) and connecting an output of theoperational amplifier to the first node for maintaining the first andsecond nodes at a common voltage potential.
 18. A method of making asclaimed in claim 17 including making the sensor and the first and secondresistances R_(S1) and R_(S2) coplanar.
 19. A method of making asclaimed in claim 18 wherein the step of making the sensor and the firstand second resistances R_(S1) and R_(S2) coplanar includes the steps of:simultaneouly depositing a single layer of material for the sensor andthe first and second resistances R_(S1) and R_(S2); and simultaneouslypatterning said single layer of material to form the sensor and thefirst and second resistances R_(S1) and R_(S2).
 20. A method of makingas claimed in claim 17 including: connecting a first side of a testinstrument for enabling a determination of resistance to the first nodeand connecting a second side of the test instrument to at least one ofthe first and second shield layers.
 21. A method of making as claimed inclaim 20 including: shorting the first and second shield layerstogether; and connecting the second side of the test instrument to eachof the first and second shield layers.
 22. A method of making as claimedin claim 21 including making the sensor and the first and secondresistances R_(S1) and R_(S2) coplanar.
 23. A method of making asclaimed in claim 22 wherein the step of making the sensor and the firstand second resistances R_(S1) and R_(S2) coplanar includes the steps of:simultaneouly depositing a single layer of material for the sensor andthe first and second resistances R_(S1) and R_(S2); and simultaneouslypatterning said single layer of material to form the sensor and thefirst and second resistances R_(S1) and R_(S2).
 24. A method of makingas claimed in claim 23 further comprising the steps of: making a writehead including the steps of: forming ferromagnetic first and second polepiece layers with a yoke portion between a pole tip portion and a backgap portion; forming a nornagnetic write gap layer between the pole tipportions of the first and second pole piece layers; forming aninsulation stack with at least one coil layer embedded therein locatedbetween the yoke portions of the first and second pole piece layers; andconnecting the first and second pole piece layers at their back gapportions.
 25. A method of making as claimed in claim 24 wherein thesecond shield layer and the first pole piece layer are formed as acommon layer.
 26. A method of making as claimed in claim 24 wherein thesecond shield layer and the first pole piece layer are formed asseparate layers; and forming a nonmagnetic insulative isolation layerbetween the second shield layer and the first pole piece layer.
 27. Amethod of making as claimed in claim 17 including: the second resistorR_(S2) further being connected between the second node and the secondshield layer; and connecting a third resistor R_(S3) between the secondnode and the first shield layer.
 28. A method of making as claimed inclaim 27 including making the sensor and the first, second and thirdresistances R_(S1), R_(S2) and R_(S3) coplanar.
 29. A method of makingas claimed in claim 28 wherein the step of making the sensor and thefirst, second and third resistances R_(S1), R_(S2) and R_(S3) includesthe steps of: simultaneouly depositing a single layer of material forthe sensor and the first, second and third resistances R_(S1), R_(S2)and R_(S3); and simultaneously patterning said single layer of materialto form the sensor and the first, second and third resistances R_(S1),R_(S2) and R_(S3).
 30. A method of making as claimed in claim 27including: connecting a first side of a test instrument for enabling adetermination of resistance to the first node and connecting a secondside of the test instrument to the first shield layer.
 31. A method ofmaking as claimed in claim 30 including making the sensor and the first,second and third resistances R_(S1), R_(S2) and R_(S3) coplanar.
 32. Amethod of making as claimed in claim 31 wherein the step of making thesensor and the first, second and third resistances R_(S1), R_(S2) andR_(S3) includes the steps of: simultaneouly depositing a single layer ofmaterial for the sensor and the first, second and third resistancesR_(S1), R_(S2) and R_(S3); and simultaneously patterning said singlelayer of material to form the sensor and the first, second and thirdresistances R_(S1), R_(S2) and R_(S3).
 33. A method of making as claimedin claim 32 wherein the second shield layer and the first pole piecelayer are formed as a common layer.
 34. A method of making as claimed inclaim 32 wherein the second shield layer and the first pole piece layerare formed as separate layers; and forming a nonmagnetic insulativeisolation layer between the second shield layer and the first pole piecelayer.
 35. A method of making as claimed in claim 27 including:connecting a first side of a test instrument for enabling adetermination of resistance to the first node and connecting a secondside of the test instrument to the second shield layer.
 36. A method ofmaking as claimed in claim 35 including making the sensor and the first,second and third resistances R_(S1), R_(S2) and R_(S3) coplanar.
 37. Amethod of making as claimed in claim 36 wherein the step of making thesensor and the first, second and third resistances R_(S1), R_(S2) andR_(S3) includes the steps of: simultaneouly depositing a single layer ofmaterial for the sensor and the first, second and third resistancesR_(S1), R_(S2) and R_(S3); and simultaneously patterning said singlelayer of material to form the sensor and the first, second and thirdresistances R_(S1), R_(S2) and R_(S3).
 38. A method of as claimed inclaim 37 wherein the second shield layer and the first pole piece layerare formed as a common layer.
 39. A method of making as claimed in claim37 wherein the second shield layer and the first pole piece layer areformed as separate layers; and forming a nonmagnetic insulativeisolation layer between the second shield layer and the first pole piecelayer.